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A role for Chk1 in blocking transcriptional elongation of p21 RNA during the S-phase checkpoint

Rachel Beckerman1, Aaron J Donner, Melissa Mattia

  • 1Department of Biological Sciences, Columbia University, New York, New York 10027, USA.

Genes & Development
|June 3, 2009
PubMed

Insights

The protein kinase Chk1 selectively blocks p21 gene transcription elongation during S-phase arrest. Ablating Chk1 restores p21 mRNA levels and transcription elongation, revealing a link between replication checkpoints and gene expression machinery.

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • Gene Expression

Background:

  • p53 target genes, including p21, are not strongly induced during S-phase arrest despite high p53 levels.
  • Reduced p21 mRNA accumulation during replication inhibition correlates with impaired transcription elongation.

Purpose of the Study:

  • To investigate the role of the protein kinase Chk1 in the S-phase-specific transcription elongation defect of the p21 gene.
  • To elucidate the link between the ATR/Chk1 replication checkpoint and transcription elongation/processing machinery.

Main Methods:

  • Utilized gene ablation of Chk1 and Chk2 in cells experiencing S-phase arrest.
  • Measured p21 mRNA levels and RNA polymerase II (RNAPII) elongation using quantitative assays.
  • Assessed the recruitment of transcription elongation and processing factors to the p21 gene locus.

Main Results:

  • Ablation of Chk1 rescued the p21 transcription elongation defect, increasing p21 mRNA levels and RNAPII presence at the 3' end of the gene.
  • Restoration of elongation factors (DSIF, CstF-64, CPSF-100) recruitment was observed upon Chk1 ablation.
  • Ablation of Chk2 did not rescue p21 mRNA levels, indicating a selective role for Chk1.

Conclusions:

  • Chk1 kinase directly and selectively mediates the transcription elongation block of p21 during S-phase arrest.
  • This study establishes a novel connection between the ATR/Chk1-mediated replication checkpoint and the regulation of transcription elongation and 3' processing.

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